Underground service pipes such as sewers which make up the utility infrastructure need replacement or rehabilitation as they age. Through normal service the lines, typically made of concrete, deteriorate or break allowing waste to escape. The buried pipes present access problems. Also, it is desirable to maintain sewer service while the replacement or rehabilitation of the sewer line takes place.
Repairing a service line can involve digging up most or all of the line and replacing the pipe. This is costly, labor intensive and disrupts normal service. Alternative methods such as pipe bursting have been developed which includes breaking up the old pipe underground and following the bursting operation with placement of new pipe in the space provided. Another alternative method involved extracting the old pipe at intervals and replacing it with new pipe by forcing the new pipe into the space provided after the extraction process. The old pipe that was extracted needed to be disposed of adding another economic factor to the method. Some of these methods utilized pipe jacking machines with hydraulic rams or mechanical drivers to push the new pipe in place. In some cases the pipe jacking equipment took up space in the excavation next to the pipe to be burst or extracted. The access thorough existing manholes was insufficient to accommodate the pipe jacking equipment.
The renewal or rehabilitation of the service lines without digging up the line was developed by inserting new pipe or slip lining with materials such as plastic pipe liners inside the old pipe. Rehabilitation of old pipe with a new internal slip lining requires cleaning the existing host pipe of debris that has built up with use. Some methods utilize stationary derricks for the cleaning operations with a drag bucket. The derricks need to be reset after each operation. The bucket size may be limited by the height of the derrick used to hoist the bucket to the surface. The pipe liner is pushed into the host pipe. Often the pressure exerted in the pushing operation is not evenly distributed causing damage to the liners.
The host pipe should be tested after the cleaning process to determine if debris has been removed and the pipe liner can fit. The new joints of liner pipe is then placed in the host pipe. The liner generally has a slightly smaller diameter than the inside of the host pipe.